Treatment of mixtures of hydrocarbons and hydrofluoric acid



prilvzs, 1944. J, D. GIBSON 2,347,317

TREATMENT OF MIXTURES OF HYDROCARBONS AND HYDROFLUORC ACID Filed April6, 1942 47 I IGI-IT GASES 26 77 62' 63 46 f ISOBUTANE CONDENSER I I9 i74 l I 46 /44 l Y l C F Z 'I 2| n: t 0 O. g -4- E 73 67 2o 26 A}27 ..7125 I 5 6 L3 72 /IQ A22/70 75 76 33 23\ BUTANE MINORI-1% I H 6I I I6ISOBIJTANE 66l 42 LZ Ooi 3i 63 62 F2 E A,/ 43 z fr OD I Q oLEI-'IN 36*QH 56| 32 C y-T-r-ALKYLATOR U 35 34 37 g LL -A "\24 65 e|\ 64HYDROFLUORIG AGID 38 t 3o 29 5l 5 39 .jo l d *7 t AI.KYI ATE\ 50 l 4| eo53 54 i LIJ Y E i I- 55 v 3 I I ,5 I I I 0i Z I z I I4 I PQ E 1 I- 3 O UI3 I o I2 II 3 ISOMERIZATION REAGTOR LID "f il Q CI:

J 56 56 82 I y I MOTOR FUEI.

INVENTOR JAMES D. GIBSON ATTORNEYS Patented Apr. VV, 1944 TREATMENT OFMIXTURES OF HYDROCAR- BONS AND HYDROFLUORIC ACID James D. Gibson,Bartlesville,

Phillips Petroleum Company,

Delaware Okla., assigner to a corporation of Application April s, 1942,serial No. 437.898

4 claims. (ci.

This invention relates to the treatment of mixtures which comprisehydrouoric acid and hydrocarbons. More particularly it relates to theproduction of hydrocarbon-hydrofluoric acid mixtures of desiredproportions. It relates iurther to the production of liquid paraiiinsfrom low-boiling normal paraiiins. l

Inprocesses in which hydrouoric acid is used as a catalyst .or reagent,such as alkylation of hydrocarbons to produce motor fuel andreconstruction of hydrocarbons -to produce other hydrocarbons havingachemical structure different from that o'the feed material, there isfrequently produced, at some stage in the process', a mixture whichcomprises hydrouoric acid and one or more saturated hydrocarbons. Often,

acid-soluble materials such as unsaturated hydrocarbons andfluorinatedorganic compounds are also present. At times it is desired to separatesuch mixtures into several fractions,'among which may be a fractioncontaining hydrofiuoric acid and one or more specic hydrocarbons, suchas isobutane or normaliy butane, in desired proportion for use in asubsequent step.

In feeds to a process such as the alkylation of isobutane in thepresence of hydrofiuoric acid as catalyst, it is desirable to have amixture of hy-A droiluoric acid and isobutane that comprises more than25 per cent hydrofluoric acid by weight; for example, acid-to-isobutaneratios of 0.421 to 4:1 or more are ordinarily needed in alkylatingsteps. l

An object of this invention is to provide an improved process forconverting relatively lowboiling hydrocarbons to motor fuel hydrocarbonsin the presence of hydrofluoric acid as a catalyst.

Another object is to produce by distillation, from a two-liquid-phasemixture comprising hydroiluoric acid and one or more hydrocarbons,

a fraction comprising hydrofiuoric acid and isobutane in controlledproportions and suitable for use as feed to an alkylating step.

Another object is to produce by distillation, from a two-liquid-phasemixture comprising hydrouoric acid and one or more hydrocarbons, afraction comprising hydrofiuoric acid and normal butane in controlledproportions and suitable for use as feed in a reconstructing orisomerizing step.

Other objects and advantages of this invention will become apparent fromthe accompanying disclosure and discussion.

In accordance with one aspect of this invention, a mixture comprisingisobutane, normal the isobutane is treated.A to produce a mixture'consisting, of hydrouoric acid and isobutane in desired proportions bydistilling the mixture while retaining the normal butane in the kettle,cooling andseparating the overhead distillate into two liquidphases,withdrawing substantially all of the lower or hydrouoric acid phase anda desired limited proportion only of the upper or -isobutane phase, andreturning the remainder of the upper phase as reflux to the distillationco1- umn. This procedure is especially advantageous in a combinationisomerization-alkylation process in which normal butane is isomerized toisobutane in the presence of hydroiluoric acid; the resulting reactionmixture is distilled; and the distilled hydroiluoric acid and isobutane,in any desiredV proportion whereby the acid-to-isobutane ratio isgreater than that in a corresponding azeotropic mixture, are passedto'an alkylating zone.

Further, in a process in which a mixture comprising normal butano,hydrocarbons boiling portion, greater than zero and less than-100 percent, of the upperor hydrocarbon phase and returning the remainder ofthe upper' phase as reiiux to the distillation column. This procedure isespecially advantageous ina combination isomerization-alkylationprocesslin which normal butane is isomerized to isobutane in the presence ofhydroiluoric acid as a catalyst: the resulting reaction mixture iscooled and separated into two liquid phases, of which the heavier orhydrofiuoric acid phase is passed as catalyst to an alkylating zone, andof which thel lighter or hydrocarbon phase is passed together with thetotal eiliuent from the alkylating zone to a fractionator; from thisfractionator an overhead azeotropic mixture of isobutane andhydrofluoric acid is passed (after depropanization if necessary) to thealkylating zone, and a kettle fraction comprising normal butane,hydrocarbons boiling above normal butane, and hydroiiuoric acid in;t

excess of that required to form an ,azeotropicf mixture with all thenormal butane, is passed to a distillation column; and the distilledhydrofiuoric acid and normal butane, in any desired proportion'wherebythe acid-to-outane ratio is greater than that in a correspondingazeotropic mixture, are passed to an isomerizing zone.

An understanding of' some aspects of my lnvention may be aided byreference to the accompanying drawing, which is a schematic iiowdiagramof one arrangement for practicing my invention in a combinationisomerizaton-alkylation process for producing motor fuel hydrocarbons.By omitting part of the equipment shown and making other minor changes,as will be described hereinafter, the process may be operated as anallgvlation process without an isomerizlng sten In the arrangementshown, a mixture of a suitable hydrocarbon, for example, normal butano,and hydrofluoric acid is admitted through inlet il, valve i2, pump I3,and heating coil I4 to reactor iii, wherein a substantial proportion ofthe normal butane is converted to insobutane, and'. to some extent, tohigher-boiling hydrocarbons, such as pentanes and hexanes.

In reactor I5, the ratio of hydroiluoric acid to hydrocarbon ispreferably in the range from about 0.2:1 to irl or more by weight;usually, operating with an, acid-to-hydrocarbon ratio within this rangewill effect the maximum conversion of normal paramns to isoparains.Preferably most of the acid comes from other steps (to be describedhereinafterL and only enough fresh or make-up acid is introduced throughinlet il to maintain a desired quantity in temperature may vary fromabout 250 to 1000 F. A temperature in the range 30o to 900 F. is usuallypreferred; at low temperatures, the rate ci reaction is low, and at hightemperatures, some cracking and carbon formation occurs. The pressuremay be within the range of about atmospheric to 5000 pounds per squareinch or more; usually, it is preferred, for reasons of economy inequipment and operating costs, to use a pressure in the range of 250 to2000 pounds per square inch. The reaction time may vary from about 1 toabout 300 minutes, depending chiefly upon the temperature. The timerequired decreases with increase in temperature. If the reaction time isvery short, such as 1 to 5 minutes, the reaction can be completed inheating coil I4 or in an extension thereof; whereupon reactor I5 may beby-passed or removed from the system. Preferably the reaction zone ispacked with a. contact mass, such as steel turnings, alumina, bauxite,or other material resistant to destruction by hydroiiuoric acid andsuitable for aiding the reaction and/or heat transfer.

The resulting mixture of hydroiiuoric acid and hydrocarbons is passedfrom reactor I5 through valve i6 and conduit Il to distillation columnI8, wherein it is subjected to distillation in accordance with thisinvention to produce, as an overhead product, a mixture of iluoric acidin which the proportion of hydroiiuoric acid is greater than that in anazeotropic mixture and which is suitable for use as feed to analkylating'step. An overhead mixture of hydrofluoric acid and isobutane(some propane may also be present at times) from the top of column I 8is cooled, liquefied, and separated into two liquid phases, as bypassing it through cooling coil I S and valve 25 to separator 2l. Thiswill be substantially an azeotropic mixture. Substanthe system. Thereaction isobutane and hydro-- junctures or polymerization reactions.

tially all of the lower or acid phase is passed through valve 22 andconduit 23 to alkylator 24, together with any desired proportion, lessthan per cent and greater than zero, of the upper or hydrocarbon phase(mostly isobutane), which is passed through valve 25, the resultantmixture passing through conduit 23 being the aforesaid overhead product.The remainder of the hydrocarbon phase is returned through valve 25 andconduit 2l as reflux to the top of column I8. If desired part of theeffluent .from cooling coil i5 may be recycled through valve 28 andconduit 2l for use as additional reflux in column I8, or a part may bepassed directly to the alkylatlon step through conduit 69 and valve 70.

The kettle fraction from column I8 comprises normal butano,motor-fuel-range hydrocarbons, small proportions of higher-boilinghydrocarbons, and acid-soluble materials; in some cases, when not allthe hydrouoric acid is distilled overhead hydrofluoric acid will also bepresent. This fraction is preferably passed through conduit 29 and valve30 to fractionator 3l for producing an overhead fraction comprisingnormal butane, which is passed through conduit 32 and valve 33 to pumpI3.

Under some conditions of operation, it is advantageous to yremovepropane and otheri rela` tively low-boiling inert material from t-hesystem by passing part of the hydrocarbon phase from the top ofseparator 2| through valve 44 and conduit 45 to depropanizer 45, fromwhich an overhead fraction comprising mainly material boiling belowinsobutane is withdrawn through outlet 41 having valve 48, and fromwhich a kettle fraction comprising mainly isobutane is passed via valvet9 and conduit 23 to alkylator 24.

In alkylator 24, the mixture of isobutane and hydrofiuoric acid is mixedunder alkylatng' conditions with an alkylating reactant, such es anolefin having from 3 to 5 carbon atoms per molecule, an alkyl compound,such as an alcohol or a halide, or an oleiinic polymer, which isintroduced through inlet 34 and valve 35.

In the total feed to alkylator 24, the weight ratio of isobutane toolefin, or other alkylating reactant, is preferably in the range of 2:1to 20:1 or more, and will generally be even higher in the reaction zone,and the weight ratio of hydrouoric acid to total hydrocarbons ispreferably in the range of 0.4:1 to 4:1. 'Ihe olen or other alkylatingreactant is preferably introduced into the reaction mixture underconditions of high turbulence and/or in multipointwise fashion, so thatit is rapidly mixed with the isobutane. This procedure is advantageousin order to favor the desired olefin-isoparaiiin junctures, oralkylation reactions, and to hinder undesirable olefin-olefin Preferredoperating conditions in alkylator 24 are a temperature in the range of30 to 150 F., a pressure suicient to maintain all components in theliquid phase, and a time of about 1 to 30 or more minutes; however,conditions outside of these ranges may also be used without passingbeyond the scope of this invention.

After asuitable reaction time, the resulting mixture passes fromalkylator 24 through conduit 36 and valve 3l to separator 38, wherein,as by cooling and gravitational or centrifugal means, it is separatedinto two liquid phases. Part of the heavier or hydrofluoric acid phasemay be recycled through valve 39 and conduit 40 to alkyla tor 24;preferably, however, most of it is passed through conduit 40 and valve4I to pump I3 for ple, in a combination isomerizatiomalkylation use ascatalyst in the isomeriaing step. The

Alighter or hydrocarbon phase from separator 33 is passed through valve@l2 and conduit 43 to column i3, in which, together with the eiiluentfrom the isomerizing step, it is separated into two frac tions asalready described. l

The kettle fraction from ractionator 3 i which comprises mainlybranched-chain motor-fuel hydrocarbons or alkylate is passed throughvalve 50 and conduit 5i to rerun column 52. In this column it isseparated into two fractions: (l) `a major motorfuel-range fraction,which is passed through valve 53 and conduit 54 to deiiuorinator l 55;and (2) a bottom fraction comprisnig hydrocarbons boiling above themotor-fuel range. which is withdrawn through outlet 56 having valve al.

Fluorine remover or deiiuorinator 55 comprises a chamber containing acontact mass having hydrogenation and/or dehydrogenation properties,such as bauxite, alumina, or other similar catalyst. Usually suitableoperating conditions are a temperature in the range or 75 to 500 F. anda space velocity in the range of. 1 to 50 volumes of liquid hydrocarbonmaterial per volume of catalyst per hour. Under such conditions, whichmay be particularly selected by trial i'or any particular case,organically combined iiuorine is substantially completely removed fromthe hydrocarbon material, which then is withdrawn through outlet 58having Valve 59.

Under some conditions other modications of the foregoing general schemewill be preferable. For example, if the available parainic feed materialcomprises appreciable proportions of isobutane, it is advantageous tointroduce this feed to column i8 through inlet 60 having valve 6i. Ifauxiliary supplies of isobutane are available, it is advantageous tointroduce them directly to alkylator-24 through inlet 62 and valve t3.If

desired, additional or make-up acid may also be introduced to alkylator24, as through inlet @d and valve 65.

My invention is also applicable to a. simple alkylation process, such asthat used if adequate supplies of isobutane are available withoutisomerization of normal butane, Such a process may also be illustratedby the accompanying drawing, with the following changes in operation:

The isobutane-containing feed material preferably is admitted throughinlet 62 having valve t3 50 to alkylator 24. Make-up hydroiiuoric acidis introduced through inlet 64 having valve d5. Part of the totaleiiluent from alkyiator 24, preferably at least one-fourth or more, isby-passed around separator 38 directly through valve S6 and conduit 43to column I8. The amount of alkylation eiiiuent so lay-passed isadjusted or regulated so that the material returning to alkylator 2dthrough conduit 23 has the desired proportion of hydroiiuoric acidneeded for the alkylation and so' that the kettle product from column I8is free from hydroiiuoric acid. Appropriate valves, such yas valves I6,33, and 44, abre closed 'to remove from use equipment not necessary tothe alkylation step. Normal butane may be withdrawn from the systemthrough outlet 61 having valve 68. Hydroiiuoric acid from the bottom ofseparator 33 is recycled through valve 39 to alkylator 24. Proceeding inthis manner has the advantage that column i8 serves to regeneratecontinuously `hydrofiuoric acid spent in the alkylation step.

Many other modications and/or applications of my invention will beobvious to those skilled in the art of hydrocarbon conversion. For examuis given:

process, similar to that already described, total eiuent from analkylator, together with hydrocarbon ei'iiuent from an isomerizing step,may beV passed to a distilling column from which an over head mixture ofhydrouoric acid and isobutane is passed or-recycled to the alkylator,and from which a kettle fraction comprising normal butane,

motor-fuel hydrocarbons, and hydroiiuoric acidv is passed to anazeotropic distilling column used in the same manner as thathereinbeiore described for column is. From this column there is producedan overhead fraction comprising hydroiiuoric acid and normal butane incontrolled proportions, such as in the range of 0.421 to 4:1 by weight,suitable for use as feed to the isomerizing step. Hydrouoric acid fromthe isomerizing step is passed as catalyst to the alkylating step. Forthis modification it is desirable to make the following changes: Columnit is operated as an ordinary azeotrope column, sending an overheadazeotropic mixture of isobutane and hydroiiuoric acid through line t9and valve l@ to alkylator 2Q; valve 28 is closed. Hydrouoric acid,normal butane, and alkylate pass from the kettle of coiumn i8 throughvalve 3d to fractionator Si, which is now operated in the manner that isa special feature of this invention. That is, valves s3 and 68 areclosed; an overhead azeotropic mixture of normal butane and hydrouoricacid is passed through line ii and valve 'i2 to condenser is, from whichit is passed through valve it to setltier or separator 1E for separationinto two liquid phases. The heavier or acid phase is passed throughvalve l5 and conduit 32 to pump i3. Any desired portion less than 100per cent of the lighter or normal butane phase is passed through valveil and conduit 32 to pump i3; the remainder of the butane phase ispassed as reiiux through valve 82 and conduit t3 to column 3l. Valve i6is closed, and the isomerizer emuent from reactor is is passed throughvalve 'i3 to separator i9, in which it is separated into two liquidphases. The lighter or hydrocarbon phase is passed through valve andconduit il to column 8; the heavier or hydrouoric acid phase is passedthrough valve El and conduit 82 for use as catalyst in alkylator 2d.

My invention is very advantageous for use in applications similar to theforegoing in that no separate acid-distilling equipment is necessary.For example, acid-soluble materials-dissolved in the acid passed intocolumn 18 remain in the kettle fraction and subsequently act to increasethe yield of motor fuel, or are` removed from the and isoparains soformed and including isopeny tane may be alkylated. In isomerlzingnormal pentane a substantial amount of isobutane is gena erally alsoproduced, and in such a case the combined isobutane and isopentane maybe subjected to alkylation.

To further illustrate some of the many laspects of my invention, thefollowing specic example In an arrangement similar to that illustratedin the accompanying drawing, normal butane and concentrated orsubstantially anhydrous hydrofluoric acid are charged to an isomerizingstep. The isomerizing conditions are approximately as follows:temperature V350" F.; pressure, 1500 pounds per square inch(liquid-phase conditions) reaction time 200 minutes; acid"to-hydrocarbonratio, 3:1 by weight. The total effluent from the isomerizing step iscooled and passed to an azeotropic distilling column having a specialrefluxlng arrangement whereby the overhead fraction is separated bycooling and gravity into two liquid phases. The lower or acid phase anda part of the upper or hydrocarbon phase are withdrawn in a weight ratioof about 2 :1; the remaining part of the upper phase is returned asreiiux to the top of the column. The hydrocarbon portion withdrawn ispassed through a depropanizer wherewith most of the propane andincidental low-boiling materials are removed by distillation; theresidual isobutane and the hydroiluoric acid withdrawn are passedtogether as feed to an alkylating step, wherein the isobutane isalkylated under alkylating conditions with an alkylating agent, such asa mixture of butylenes The conditions in the alkylator are as follows:temperature 90 to 115 F.; pressure, 125 to 175 pounds per square inch;average reaction time, 6 minutes, rapid agitation to maintain intimatecontact between acid and hydrocarbon phases, isobutane-to-alkylatingagent ratio, about 6:1 by weight, acid-to-hydrocarbon ratio, about 2:1by weight.

The resulting eilluent mixture from the alkylator is passed to a settlerin which it is separated into an acid phase and a hydrocarbon phase. Theacid phase is passed to the isomerizing step for use as catalyst, andthe hydrocarbon phase, which comprises isobutane and motor-fuelhydrocarbons, is passed to the aforementioned azeotropio distlilingcommu. From the bottom of this column motor-fuel hydrocarbons producedby alkylation, together with normal butane and higher-boilinghydrocarbons originating in the isomerizing step, are passed to adebutanizing column for separating normal butane, which is recycled tothe isomerizing step. The remaining material, which is mainly highlybranched parafnic hydrocarbons suitable for use in aviation gasoline, issubjected to another distillation step` to remove relativelyhigh-boiling impurities, and to a defluorination treatment to removeorganic fluorine. 'Ihe resulting motor-duel fraction is substantiallycompletely saturated, has a clear octane number of about 91, and issuitable for use in aviation gasoline It is not intended that mentionci' specic apparatus or of specific applications should be taken tolimit unduly the scope of my invention. The special distilling andrefluxing features of my invention are applicable, for example, to anycase wherein it is desired to produce a distillation product ofcontrolled proportions of a low-boiling saturated-type hydrocarbon andhydrofluoric acid in which product the proportion of hydrouoric acid isgreater than that in a corresponding azeo.. tropic mixture. Theinvention should no-t be limited otherwise than as specified in theappended claims.

What I claim is:

A1. In a combination isomerization-alkylation process in which there isproduced a mixture comprising isobutane, normal butane, hydrocarbonsboiling higher than normal butane, and hydrou fluoric acid in excess ofthat required to form azeotropic mixtureswith al1 the isobutane and withall the normal butane, the steps which comprise distilling the mixtureto produce an over? head azeotropic mixture comprising isobutane andhydrofiuoric acid and a bottom fraction comprising normal butane,hydrocarbons boiling higher than normal butane, and hydrofiuoric acid inexcess of that required to form an azeotropic mixture with all thenormal butane; passing said overhead azeotropic mixture comprisingisobutane and hydrofluoric acid to an alkylating zone; passing saidbottom fraction to a second distilling column and distilling 'anazeotroplc mixture of hydrofiuoric acid and normal butane overhead andretaining hydrocarbons boiling higher than normal butane in the kettle;cooling and separating the overhead distillate into two liquid phases,withdrawing substantially all of the hydrouoric acid phase and asubstantial proportion of the ture comprising isobutane and hydrofluoricacid is distilled overhead and normal butane is retained vin the kettle;cooling and separating the overhead distillate into two liquid phases,withdrawing substantially all of the hydroiluoric acid phase and asubstantial proportion of the isobutane phase;v passing these withdrawnmaterials to an alkylating zone; and returning the remainder of theisobutane phase as reflux to the distillation column.

3. In a process for isom'erizing normal butane to form isobutane and foralkylating isobutane so formed, the improvement which comprisesisomerizing normal butane in the presence of concentrated hydroiiuoricacid as the isomerization "catalyst to form isobutane, passing eiiluentsof said isomerizatlon to a fractional distillation column, removing fromsaid fractional a` low-boiling mixture comprising isobutane andhydrofluoric acid, cooling and condensing at least a portion of saidmixture to form a liquid isobutane phase and a liquid hydrofluoric acidphase, returning a portion of said liquid isobutane phase to saidfractional distillation column, passing a further portion of saidisobutane phase together' with said hydroiluoric acid to an alkylationzone, reacting said isobutane with an added alkylation reactant in thepresence of said hydroiiuoric acid as the alkylation catalyst,separating from eilluents of said alkylation a maior part of thehydroiiuoric acid, passing a residual hydrocarbon material containingonly a minor part of hydrouoric acid to said fractional distillationcolumn, and removing as a high boiling traction from said fractiona1distillation column a hydrocarbonfmaterial substantially free fromisobutane 4. In a process for isomerizing a low-boiling normal parafiinof at least four carbon atoms per molecule and for alkylating resultinglow-boiling isoparains, the improvement which comprises isomerizing alow-boiling normal paramn of at least four carbon atoms per molecule inthe presence of concentrated hydrouoric acid as the isomerizationcatalyst to form low-boiling isoparaiiins, passing etlluents of saidlsomerization to a,

distillation column zone a hydrocarbon material substantially free fromhydroiiuorlc acid, passing said hydrocarbon material to the aforesaidfractional distillation means, and recovering also from saiddistillation s means a normally liquid isoparaiiinic hydrocarboniractional distillation means, passing from said distillation means toan alkylating zone a lown boiling isoparain and hydroiiuoric acid,reacting in said alkylation zone said isoparamn with an added alkylatingreactant in the presence of said hydrouoric acid to form higher-boilingisopaxains, separating from eiiluents of said alkylation material soproduced.

JAMES D. GIBSON.

